Catalyst compositions based upon a Group IVA metal compound of the general formula (Cp).sub.2 MeX.sub.2 wherein Cp represents identical or different cyclopentadienyl groups which may be substituted with one or more alkyl groups, Me represents a Group IVA metal and X represents halogen substituents attached to the Group IVA metal, and an aluminoxane are known. Further, the use of such catalyst compositions in the polymerization of one or more alpha-olefins is known from EP-A-283739.
In order to be effective in the polymerization, the known catalyst compositions contain a relatively large amount of the aluminoxane component. Such polymers typically contain a high amount of residual catalyst and further, the polymerization process is not cost effective.
The polymerization of alpha-olefins having at least three carbon atoms with a catalyst composition having cyclopentadienyl groups which are mono-, di-, tri- or tetraalkyl substituted, producing polyolefin polymers having a vinylidene end group are known. When propylene or butene-1 are polymerized, the polymer end group is of the formula --C(CH.sub.3).dbd.CH.sub.2 or --C(C.sub.2 H.sub.5).dbd.CH.sub.2, respectively. The application of polymers having a vinylidene end group, as an intermediate in the preparation of additives for lubricating oil compositions is the subject of the European patent application 0490454.
Various documents, such as EP-A-129368, EP-A-226463, EP-A-128046 and EP-A-260999, disclose polymerization catalyst compositions containing cyclopentadienyl Group IVA metal compounds and an aluminoxane. These documents teach that the cyclopentadienyl groups can be unsubstituted or substituted with a wide variety of hydrocarbyl groups, such as alkyl, arylalkyl, alkenyl, aryl and alkylaryl, but they do not indicate a preference for aryl or alkylaryl groups. For example, they do not contain any example of compounds with an aryl or alkylaryl substituted cyclopenta-dienyl group. The documents further teach that any number of alkyl groups can be present on the cyclopentadienyl group. For example, bis(cyclopentadienyl)zirconium compounds can have alkyl, dialkyl, trialkyl, tetraalkyl or pentaalkyl substituted cyclopentadienyl groups.
Although there are many well known high activity catalysts, it is still desired to improve the activity of the catalyst and produce polymers having a vinylidene substituent.